regex.3: Improve REG_STARTEND

Explicitly spell out the ranges involved. The original wording always
confused me, but it's actually very sane.

Remove "this doesn't change R_NOTBOL & R_NEWLINE" ‒ so does it change
R_NOTEOL? No. That's weird and confusing.

String largeness doesn't matter, known-lengthness does.

Explicitly spell out the influence on returned matches
(relative to string, not start of range).

Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Signed-off-by: Alejandro Colomar <alx@kernel.org>

diff --git a/man3/regex.3 b/man3/regex.3
index 47fe661d2db2726778eb7572cfdc2ff9c7274e1c..e91504986adc3f6f8597a9a9ac04687e27696c20 100644 (file)
--- a/man3/regex.3
+++ b/man3/regex.3
@@ -131,23 +131,26 @@ compilation flag
 above).
 .TP
 .B REG_STARTEND
-Use
-.I pmatch[0]
-on the input string, starting at byte
-.I pmatch[0].rm_so
-and ending before byte
-.IR pmatch[0].rm_eo .
+Match
+.RI [ "string + pmatch[0].rm_so" , " string + pmatch[0].rm_eo" )
+instead of
+.RI [ string , " string + strlen(string)" ).
 This allows matching embedded NUL bytes
 and avoids a
 .BR strlen (3)
-on large strings.
-It does not use
+on known-length strings.
+If any matches are returned
+.RB ( REG_NOSUB
+wasn't passed to
+.BR regcomp (),
+the match succeeded, and
 .I nmatch
-on input, and does not change
-.B REG_NOTBOL
-or
-.B REG_NEWLINE
-processing.
+> 0), they overwrite
+.I pmatch
+as usual, and the match offsets remain relative to
+.I string
+(not
+.IR "string + pmatch[0].rm_so" ).
 This flag is a BSD extension, not present in POSIX.
 .SS Match offsets
 Unless